The present invention relates to a video signal processing system for changing the shape of a video image so that a video frame appears to take the form of a three dimensional object. Systems of this type are disclosed in United Kingdom Patent Application Nos. 2119594A and 2158671A assigned to the assignee of the present application. These systems receive video signals, at video rate, representing sequences of images which are manipulated to produce images of a different shape to the input image. The type of processing used to produce this manipulation is called write side interpolation in which incoming picture point signals are written into addresses in a framestore, determined by the shape of the final image, and read out in normal raster format. The write addresses are pre-calculated and provide a coarse map of addresses for, say, every fourth pixel in every fourth line of every fourth field. These coarse maps can themselves be manipulated to produce a change in position or orientation in space.
As input video signals are received by the system the coarse maps are interpolated to provide the intervening addresses. In practice the write addresses do not generally fall on framestore addresses so one incoming picture point signal makes contributions to the nearest framestore addresses to the write address provided. The video signals are also interpolated and written into the desired addresses. When the contents of the frame store are read out in normal raster format the video images appear at video rate as before but the shape of the image has been changed.
Although the shape manipulation of this system is effective there is no allowance for shading from different light sources and some details of the shape may be lost particularly where there is a lot of detail in the video. It is therefore an object of the present invention to provide a system for providing shape manipulation which is capable of producing the effect of light shading on manipulated image shapes.